Scanner systems have been widely used in recent years in the printing field. Various light sources have been used in practice in recording apparatuses for image forming purposes in which a scanner system is employed. Of these, the He--Ne laser is superior in terms of stability and image quality, and it is widely used. The exposure time is short at 10.sup.-3 to 10.sup.-7 seconds per scanning exposure, and so the photosensitive materials which are used must have a high photographic speed and a high contrast, even with such a short exposure time.
Moreover, a demand has arisen in the printing industry in recent years for speeding-up operation and increasing efficiency, and higher speed scanning and more rapid processing of the photosensitive materials are very desirable. Furthermore, reductions in the amounts of developer and fixer which are used for processing is desirable from the viewpoints of storage and waste-recovery costs and from the viewpoint of environmental problems, and there are high expectations of reductions being made in rates of replenishment.
Photosensitive materials which contain carbocyanine or rhodacyanine spectrally sensitizing dyes and in which the gelatin content of the emulsion and the protective layers is specified have been disclosed in JP-A-3-59637 as such sensitive materials suitable for rapid processing and an He--Ne light source. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application".) Furthermore, silver chlorobromide emulsions which contain iridium and rhodium and which have been gold/sulfur sensitized are disclosed in the illustrative examples of that reference. However, although the results are satisfactory in terms of gradation and residual coloration with the abovementioned materials, the photographic speed is low, and satisfactory stability of photographic properties under conditions of a reduced rate of replenishment of the processing liquids has not yet been achieved.
Furthermore, silver halide photosensitive materials which contain water soluble iridium compounds have been disclosed in JP-B-57-22090. (The term "JP-B" as used herein signifies an "examined Japanese patent publication".) However, there are no known cases in which a rhodacyanine which has a specified structure like that in the present invention is used.